1.Field of the Invention
This invention generally relates to decorative body driving mechanisms, the decorative body driving mechanism having a decorative body in a main body thereof and at least one openable and closable door arranged in front of the decorative body so that the door can be opened at a given time to make the decorative body come out, and more particularly, to a decorative body driving mechanism which is capable of opening and closing at least one openable and closable door and operating the decorative body with a single motor.
2.Description of the Related Art
Conventionally, a timepiece having a decorative body therein has been well known. The timepiece opens the door to make the decorative body come out at given times such as the hour and make the decorative body move for a certain period of time, for example, with music, and then closes the door to house the decorative body. The aforementioned timepiece having the decorative body needs a source of power to open and close the door and operate the decorative body. In other words, the above-mentioned timepiece requires the motors equal in number to objects to be operated, whereas the normal timepiece displays the time only. It is to be noted that the production cost increase as the number of motors increases. In addition, a space has to be made for the motors, and accordingly the timepiece becomes larger.
Japanese Patent Application Publication No. 8-68869 (hereinafter referred to as Document 1) proposes a mechanism for opening and closing a door of a timepiece having a decorative body therein, the mechanism being capable of opening and closing the door and operating the decorative body with a single motor. This mechanism includes a first gear and a second gear disposed coaxially, and the second gear is bonded to slip. The motor is configured to rotate the first gear by way of a decelerating gear train, and the coaxially disposed second gear rotates to open and close the door. Additionally, a stopper is provided at a fully opened position of the door. Further, the mechanism is configured to include a drive transmission gear engaged with any one of the decelerating gear train or the first gear. The drive transmission gear thus operates the decorative body.
The mechanism of Document 1 includes the two gears that are coaxially disposed and bonded to slip. When the door stops at the fully opened position, slipping between the two gears can maintain the rotation of the motor. Therefore, even after the door stops at the fully opened position, the rotational force of the motor can be transmitted to the drive transmission gear to maintain the movement of the decorative body.
The mechanism of Document 1,however, continuously generates the force to open the door even after the door fully opens. This is why the two gears are slipped to release the aforementioned force. However, if the two gears are slipped in this manner, the contact part will be worn and will easily be slipped more than ever. This makes it difficult to rotate the two gears simultaneously with the use of friction, resulting in a problem in that the door cannot be opened or closed accurately. Moreover, there arises another problem in that the slipped gears make a friction sound and this disturbing noise damages the musical performance while the decorative body is moving with music. Besides, the motor is always connected with the gear that opens and closes the door in the mechanism of Document 1.Therefore, when the rotation of the motor is changed to close the door, the door starts to close immediately. The rotational direction of the motor is thus limited, and this arises yet another problem in that the performance made by the decorative body is limited to a monotonous action such as a rotation in one direction or the like.